Radiator support, some brackets, and hardware (just soem other things not mentioned and still doesnt encompass the entire swap). It can, and HAS been done, but its not cheap at all unless you can do ALOT of the work yourself.

A minute later: Hmm, it would look interesting. I have a feeling that swap is much more involved than a swap between the different second generation (02-07) models, but with enough time and money, it could probably be done.

After some more thought: I don't think the front lines of a third gen (08+) impreza would look good with the rest of the lines of a second gen. You're crazy, man... just crazy.